It is known that for the cooling and/or lubrication of the compressor element use is made of oil that is injected into the housing of the compressor element.
This oil is guided around by means of an oil circuit through the compressor device.
To be able to inject the oil, the oil circuit is provided with an oil pump.
This oil pomp is driven by means of the aforementioned drive that drives the rotor.
When the compressor device is switched off, whereby the speed of the motor decreases, the oil pump will also be switched off so that no oil is injected.
However, when switching off the compressor device it is important that sufficient oil is still injected for some time.
Also when starting up the compressor device it is important that before the rotor comes into operation, the oil can already circulate to lubricate the compressor element.
In order to provide an oil supply in these situations, in known installations an additional ancillary pump with a separate drive is provided.
This auxiliary pump will come into operation when switching off and before starting up the drive of the rotor in order to provide the necessary oil injection.
Such known installations also present the disadvantage that an additional auxiliary pump and auxiliary motor must be provided, whereby separate inlet and outlet pipes have to be provided.
Another disadvantage is that non-return valves must be provided in order to counteract a backflow of oil when one of the pumps is switched off.
An additional disadvantage is that when starting up, an overpressure can occur in the oil circuit. Indeed, at the moment that the drive comes into operation, the pump will also come into operation and the auxiliary pump must be switched off. As a result too great a quantity of oil will be pumped around and injected.
Moreover, the changeover betters the pump and the auxiliary pump will cause a change in the oil supply.